GB2176235A

GB2176235A - Ball joint

Info

Publication number: GB2176235A
Application number: GB08613368A
Authority: GB
Inventors: Kanji Kubo
Original assignee: Honda Motor Co Ltd
Current assignee: Honda Motor Co Ltd
Priority date: 1985-06-03
Filing date: 1986-06-03
Publication date: 1986-12-17
Also published as: JPH0135062Y2; GB2176235B; FR2582757B1; FR2582757A1; US4650362A; JPS61198726U; DE3618565A1; GB8613368D0

Abstract

A ball joint 9 for mutually rotatably inter-connecting two members 12, 5, the ball joint including a ball shaft 35 attached to one (12) of said members, the ball shaft having at one end thereof a ball 34 rotatably received in a housing 31 attached to the other (5) of said members, and a dust boot 50 fitted on the ball shaft to surround the same, the dust boot being fixedly attached at one end thereof to the housing 31 and formed at the other end thereof with a seal lip 54 adapted to elastically engage the said one member 12, the dust boot having a projecting portion 53 surrounding the seal lip 54 and facing the said one member 12, a labyrinth S being defined between the projecting portion and the said one member. <IMAGE>

Description

1

SPECIFICATION

Ball joint This invention generally relates to a ball joint, 70 particularly but not exclusively one which is suitable for use in an independent suspension for a vehicle.

In general, as a joint for connecting two members to each other, universal joints, ball joints and the like are known. Among such joints, ball joints are known which consist of a ball shaft having a ball formed at one end thereof, the ball shaft being attached to one of two members to be interconnected with each other by the joint, and a ball housing accommodating the ball therein, the ball hous ing being attached to the other member.

Further, in recent years, in the field of sus pension for vehicles, and in particular indepen dent suspensions, there have been proposed ball joint type independent suspensions em ploying ball joints in place of the king pins that had been previously employed.

As an example of a known ball joint in such 90 a ball joint type independent suspension, there is shown in Fig. 5 a ball joint 100 in which a ball housing and a ball are arranged to be rotatable relative to each other only about the axis of a ball shaft, to thereby achieve advantages in relation to sealing and durability. The ball joint 100 includes a sealing structure corn prising a dust boot 105 that extends between a member 103 to which a shaft portion 102 of the ball 101 is fixed, and a housing 104 attached to another member (not shown), so as to cover the shaft portion 102. In Fig. 5 upward and downward directions thereof correspond to frontward and rearward directions of a vehicle.

The dust boot 105 is fixedly attached at the rear end (the lower end in Fig. 5) thereof, by a stop ring 108 embedded therein, to the outer circumference of the front part of the housing 104, and has at the front end (the upper end in Fig. 5) thereof a portion which is fitted along the inner circumference thereof on the shaft portion 102. In this front end portion is embedded an annular core member 107, and a forwardly directed annular seal lip 106 115 is formed on an outer circumferential part of the front end portion of the dust boot to face the member 103 to which the shaft portion 102 is fixed. In Fig. 5, 104a is a ball collar which is fitted tightly so as to cause the ball 120 101 to be rotatable only about the axis of the shaft portion 102 thereof with respect to the housing 104. In practice the member 103 would be a knuckle arm in a suspension, and the member that the housing 104 is attached to would be an upper or a lower arm of the suspension.

By such an arrangement, the member 103 is adapted to be rotatable relative to the member that the housing 104 is attached to, 130 GB2176235A 1 about the axis of the ball shaft.

However, the sea[ lip 106 of the dust boot 105 is arranged merely to elastically engage the side member 103 due to the flexibility thereof. In this respect, since the ball joint 100 is disposed in the vicinity of a wheel in the suspension of the vehicle, the seal lip 106 is likely to receive foreign matter such as pebbles, thus raising a problem in that the sealing of the ball 101 may be affected. Particularly, as the seal lip 106 deteriorates with time, such problem becomes significant, resulting in the possibility that problems may arise in regard to the durability of the ball joint 100 itself.

According to the present invention there is provided a ball joint for mutually rotatably interconnecting two members, said ball joint comprising a ball shaft provided with a ball at one end thereof and attachable to one of said two members, a housing attachable to the other of said two members and rotatably accommodating said ball therein, and a dust boot fitted on said ball shaft to surround the same, said dust boot having one end portion fixedly attached to said housing and another end portion formed with a seal lip surrounding said ball shaft and arranged to elastically engage said one member, said dust boot having a projecting portion surrounding said seal lip and arranged to face said one member so that a labyrinth may be defined between said projecting portion and said one member.

An embodiment of the invention will now be described by way of example and with reference to the accompanying drawings, in which:

Fig. 1 is a view of an independent rear suspension of a vehicle, as seen from the front of the vehicle at a transversely inclined angle, the suspension employing a ball joint according to a preferred embodiment of the present invention; Fig. 2 is a schematic plan view of the en- tirety of the ball joint; Fig. 3 is an enlarged horizontal sectional view of an intermediate portion and a rear portion of the ball joint; Fig. 4 is an enlarged horizontal sectional view of a front portion of the ball joint; and Fig. 5 is a horizontal sectional view of a conventional ball joint, as already described.

Referring first to Fig. 1, designated at reference number 20 is a rear independent suspension of a vehicle (not shown) that employs a ball joint 9 according to a preferred embodiment of the present invention. Fig. 1 is a perspective view of the suspension 20, as seen transversely from the front of the vehicle.

The suspension 20 includes a knuckle 1. On the knuckle 1, the lower part has on the transversely outer face thereo an axle 11 projecting therefrom to rotatably support a wheel 2, and at the front and rear sides thereof a pair of lower arms 3, 4 pivotably connected 2 GB2176235A 2 thereto, respectively. Moreover, on the upper part of the knuckle 1 there is integrally provided a knuckle arm 12, which is rearwardly and transversely inwardly curved and to the upper end of which an upper arm 5 is pivotably connected through a ball joint 9. Further, on the front part of the knuckle 1 there is formed a bifurcate portion 19 projecting therefrom, which portion 19 is fastened by bolting to a bifurcate portion 6b at the rear end of a trailing arm 6 of plate form having both faces thereof vertically oriented. By such means, the knuckle 1 is firmly united with the trailing arm 6.

In the foregoing arrangement, the trailing arm 6 comprises a plate spring member high in rigidity in the plate face direction and sufficient in elasticity in the plate thickness direction. The lower arms 3, 4 are vertically swin- gably pivoted at pivot points 3a, 4a thereof on a vehicle body frame (not shown). The upper arm 5 has a swing pivot 5a thereof fixed to a bracket 7a on a wheel housing 7 provided at the side of the vehicle body. Between the lower part of the knuckle 1 and the vehicle body is interposed a hydraulic shock absorber 8.

The rear independent suspension 20 is arranged such that the trailing arm 6 has at the vehicle body side a pivot point 6a thereof lying on the centerline L, of the swing pivot 5a, that is the swing centerline of the upper arm 5 at the vehicle body side; further, this centerline L, is parallel with the axis line L, of the ball joint 9, that is the swing centreline of the upper arm 5 at the knuckle 1 side.

Thus the trailing arm 6 is firmly united with the knuckle 1, and therefore the knuckle 1 is adapted to integrally rotate with the trailing arm 6 about the vehicle body side pivot point 6a of the trailing arm. Moreover, since the vehicle body side pivot point 6a of the trailing arm 6 is located on the vehicle body side swing centreline L, of the upper arm 5, it follows that a triangular plane 6a-5a-5c, defined by the vehicle body side pivot point 6a of the trailing arm 6, pivot point 5b of the upper arm 5 at the vehicle body side, and the pivot point of this arm 5 at the knuckle 1 side, is adapted to swing about the swing centerline L, at the vehicle body side of the upper arm 5. Accordingly, those relative angle variations between the upper arm 5 and the knuckle arm 12 which are attendant on verti- cal movements of the wheel 2, are limited to a small range. In other words, those rotary motions which take place in the body of the ball joint 9 interposed between the knuckle 1 and the upper arm 5 are restricted as far as possible.

Further, the axis line L, of the ball joint 9 is parallel with the vehicle body side swing centerline of the upper arm 5 so that rotary motions in the body of the ball joint 9 take place substantially only about the axis line L2 of the joint 9. Therefore, the independent suspension 20 itself is of a form that is excellent for sealing purposes of the ball joint, and in endurability and cost.

A preferred embodiment of the ball joint 9 will now be described with reference to Figs. 2 to 4. Incidentally, in Figs. 2 to 4, upward and downward directions thereof correspond to frontward and rearward directions of the vehicle, respectively.

The ball joint 9 includes a housing 31 in which ball 34 is received, the housing 31 being fixed around the outer circumference of an intermediate part thereof to the upper arm 5 by means of a circlip 33 cooperating with a flange 32 formed on the outer circumference of the lower part of the housing 31. In Fig. 3, 3 1 a is a ball collar that is fitted tightly so as to cause the ball 34 to be rotatable only about the axis of a ball shaft 35, as a shaft portion thereof, with respect to the housing 3 1. In this respect, the ball 34 has on the rear face thereof a shaft 34a projecting coaxially with the ball shaft 35, the shaft 34a co- operating with a correspondent recess 31b of the collar 3 1 a to thereby permit the ball 34 to rotate only about the axis of the shaft portion 35 thereof, which is the axis line L, of the ball joint 9.

On the other hand, the ball shaft 35, with the lower part of which the ball 34 is integrally formed, is formed along an intermediate part thereof with a taper surface 36 which is fitted in a tapered insertion hole 13 extending through the knuckle arm 12. Moreover, the forward end of the ball shaft 35 is formed as a threaded portion 37 on which, as shown in Fig. 4, a crown nut 38 is engaged, the nut 38 being held against rotation by means of a split pin 39 inserted through a pin hole 37a of the threaded portion 37. The threaded portion 37 is further covered with a cap-like cover 16 which is secured by bolts 15 to the front side of the knuckle arm 12. By the cover 16, ef- fective protection is provided for the threaded portion 37, the crown nut 38, and the split pin 39. The cover 16 is formed with a drain hole 17; in the mounted position of the ball joint 9, the drain hole 17 is downwardly in- clined as shown in Fig. 1.

In addition to the foregoing, the ball joint 9 has a tubular flexible dust boot 50 fitted on the ball shaft 35 so as to surround the same, thus covering the section between the housing 31 and the knuckle arm 12. The dust boot 50 has at the rear end thereof a stop ring 55 embedded therein for air-tightly securing the whole circumference of the rear end part of the boot 50 to the housing 31 in a fixed manner, and at the front end of the dust boot an annular core member 56 is partially embedded therein and fits on the outer circumference of the ball shaft 35. Moreover, at the intermediate part of the dust boot 50, on the inner circumference thereof, are formed a pair 3 GB2176235A 3 of inner annular seal lips 51, 52 axially spaced apart from each other, which seal lips 51, 52 make elastic contact with the outer circumfer ence of the root part of the ball shaft 35.

Further, externally of the seal lips 51, 52, there is provided a tightening spring 59.

The dust boot 50 has formed on the front part thereof an annular projecting portion 53 which encloses a projection 57 formed on the outer circumference of the annular core mem ber 56. The annular projected portion 53 also has formed at the inner circumference thereof a front annular seal lip 54 that is arranged to surround the whole circumference of an inner base portion 58 of the annular core member 56, thus surrounding the whole circumference of the ball shaft 35, and elastically contacting the knuckle arm 12. Thus the whole circum ference of the annular seal lip 54 is sur rounded by the annular projecting portion 53 85 of the dust boot 50.

On the other hand, in the rear face of the nuckle arm 12 that the annular projecting por tion 53 of the dust boot 50 faces, there is formed an annular recess 14 in which the an nular projecting portion 53 freely fits, with a predetermined gap left therebetween.

Thus the rear end of the dust boot 50 is arranged to be fixedly attached by the stop ring 55 to the outer circumference of the front 95 part of the housing 31, whilst its front end is arranged to be fitted, through the annular core member 56, on the outer circumference of the base part of the ball shaft 35. Moreover, in the assembled state of the ball joint 9, the front annular seal lip 54 and the front face of the annular core member 56 are engaged un der pressure with the rear face of the knuckle arm 12, whilst the inner annular seal lips 51, 52 are elastically engaged with the outer cir- 105 cumference of the ball shaft 35. Furthermore, between the annular projecting portion 53 at the front of the dust boot 50 and the annular recess 14 in the rear face of the knuckle arm 12 there is defined a narrow labyrinth S.

Of the annular seal lips 51, 52 formed on the inner circumference of the dust boot 50, the front one 51 is adapted to serve as a main lip, and the rear one 52 as a grease seal for the housing 31. The annular seal lip 54 115 formed on the inner circumference at the front of the dust boot 50 is adapted to serve as a dust seal. The inner base portion 58 of the annular core member 56 is adapted for cen tering the dust boot 50, while functioning as a 120 bearing relative to the ball shaft 35, and con currently serves also as a dust seal for the ball shaft 35 itself.

As will be understood from the foregoing description, in the ball joint 9 of the present embodiment, the annular projecting portion 53 is formed so as to surround the whole circumference of the seal lip 54 at the front end of the dust boot 50, outside of the seal lip 54, whilst the labyrinth S is defined by the annular projecting portion 53 and the annular recess 14 in the knuckle arm 12.

Accordingly, the labyrinth S, located between the seal lip 54 and the outside of the dust boot 50, acts to prevent the intrusion of foreign matter such as pebbles into the ball joint 9, as it is disposed in the vicinity of the wheel 2, and particularly to prevent pebbles and the like from being caught at the seal lip 54. Besides, in the annular projecting portion 53 which cooperates with the annular recess 14 to define the labyrinth S, there is incorporated the projection 57 that is formed on the outer circumference of the annular core mem- ber 56. As a result, due to the reinforcing effect of the core member 56, the labyrinth S keeps a desired configuration thereof and is not deformed with time, thus successfully preventing the ingress of foreign matter. Thus the sealability and endurability of the seal lip 54 is greatly improved.

Incidentally, although in the illustrated em bodiment an annular recess 14 is formed in the knuckle arm 12 to define the labyrinth S, in an alternative arrangement the annular projecting portion 53 of the dust boot 50 may be configured to cooperate with the rear face of the knuckle arm 12 to form a suitable labyrinth gap therebetween, without having the annular recess 14.

Moreover, the seal lip 54, the projecting portion 53, and the recess 14 need not necessarily be of annular form, as they may be of any other suitable form such as a requ100 lar hexagon.

Further, although in the foregoing embodiment the present invention is applied to a ball joint of a ball joint type rear independent suspension for a vehicle, it should be understood that the invention may be applied to any other ball joint that is intended to mutually rotatably unite two members with each other.

It is to be clearly understood that there are no particular features of the foregoing specifi- cation, or of any claims appended hereto, which are at present regarded as being essential to the performance of the present invention, and that any one or more of such features or combinations thereof may therefore be 6cluded in, added to, omitted from or deleted from any of such claims if and when amended during the prosecution of this application or in the filing or prosecution of any divisional application based thereon.

Claims

1. A ball joint for mutually rotatably interconnecting two members, said ball joint cornprising a ball shaft provided with a ball at one end thereof and attachable to one of said two members, a housing attachable to the other of said two members and rotatably accommodating said ball therein, and a dust boot fitted on said ball shaft to surround the same, said dust boot having one end portion fixedly attached 4 GB2176235A 4 to said housing and another end portion formed with a seal lip surrounding said ball shaft and arranged to elastically engage said one member, said dust boot having a projecting portion surrounding said seal lip and arranged to face said one member so that a labyrinth may be defined between said projecting portion and said one member.

2. A ball joint according to claim 1, wherein said ball is accommodated in said housing in such manner as to be rotatable about the axis of said ball shaft.

3. A ball joint according to claim 1 or 2, wherein the whole circumference of said one end portion of said dust boot is fixedly attached to said housing, said seal lip of said dust boot is adapted to surround the whole circumference of said ball shaft, and said projecting portion of said dust boot is adapted to surround the whole circumference of said seal lip.

4. A ball joint according to any preceding claim, wherein said dust boot includes a core member embedded in said projecting portion thereof.

5. A hall joint according to any preceding claim, wherein said dust boot has on the inner circumference of an axially intermediate portion thereof two seal lips axially spaced apart from each other and elastically engaging the outer circumference of said ball shaft, and a tightening spring surrounding said seal lips.

6. A ball joint according to any preceding claim, in combination with said one member, wherein said one member is formed with a recess which receives said projecting portion of said dust boot therein with a predetermined gap so that said labyrinth is cooperatively defined by said recess and said projecting por- tion.

7. A combination according to claim 6, wherein said seal lip of said dust boot is annular, said projecting portion of said dust boot is annular, and said recess in said one mem- ber is annular.

8. A combination according to claim 6 or 7, wherein said ball shaft is inserted through said one member and has a portion thereof exposed beyond said one member and covered with a cover.

9. A ball joint substantially as hereinbefore described with reference to Figures 1 to 4 of the accompanying drawings.

Printed in the United Kingdom for Her Majesty's Stationery Office. Dd 8818935, 1986, 4235 Published at The Patent Office, 25 Southampton Buildings. London, WC2A 1 AY, from which copies may be obtained-